It is of importance to perform impedance matching between input and output impedance of a semiconductor element and characteristic impedance of a signal wire on a wiring board. If the impedance matching is not sufficiently conducted, an electric signal transmitted through the signal wire is reflected, and a waveform of the signal is disturbed, which leads to a malfunction of a semiconductor element. It is therefore desired to carry out the impedance matching between the input and output impedance of the semiconductor element and the characteristic impedance of the signal wire. Further, a so-called decoupling capacitor is disposed in the vicinity of the semiconductor element in order to supply the power to the semiconductor element and to restrain noises of the power supply, thereby stabilizing an electric potential of the power supply (which will hereinafter be referred to as a power potential or a supply voltage) and a ground potential for the semiconductor element.    [Patent document 1] Japanese Laid-open Patent Publication No. 03-223371    [Patent document 2] Japanese Laid-open Patent Publication No. 2005-191142